Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.35	5.121%	$221.122	$221.12	$221.10	$221.10
Purchase #2	$67.34	6.179%	$71.5009	$71.50	$71.50	$71.50
Purchase #3	$53.72	10.177%	$59.1871	$59.19	$59.20	$59.20
Purchase #4	$190.36	10.738%	$210.8009	$210.80	$210.80	$210.80
Purchase #5	$36.93	9.804%	$40.5506	$40.55	$40.55	$40.60
Purchase #6	$6.90	10.738%	$7.6409	$7.64	$7.65	$7.60
Purchase #7	$229.77	4.326%	$239.7099	$239.71	$239.70	$239.70
7 purchase totals =	$795.37		$850.5123	$850.51	$850.50	$850.50